Monte,
I believe that Tracy is correct if you want any kind of reasonable fuel flow. If WW 2 had gone on longer the. F8F might have been the most successful fighter. The big radials were the toughest engines flying. But the Merlin powered fighters were MUCH more efficient. If you want the range to fly to Berlin you don't choose a big radial. The mission decides the choice. The ability to add effective area to a water cooled engine does make it easier to cool if you work with the knowledge of the approximate volume needed to begin with. IMHO.
Bill Jepson
------Original Message------
From: MONTY ROBERTS
Sender: Rotary motors in aircraft
To: Rotary motors in aircraft
ReplyTo: Rotary motors in aircraft
Subject: [FlyRotary] Meredith Effect - Spitfire
Sent: Dec 24, 2009 2:17 PM

Tracy   I also forgot to mention that you aren't quite right about the less surface area thing. Although less surface area is needed the, convection coefficient along with the surface temp dictates surface area required. That can be influenced by turbulence, fluid velocity, surface condition etc.   The mass flow of air required is unfortunately directly governed by the temperature difference. No way around that one. It is simply a function of the specific heat of air, temp difference, and the amount of heat rejected.   Monty   ----- Original Message ----- From: Tracy Crook To: Rotary motors in aircraft Sent: Thursday, December 24, 2009 3:23 PM Subject: [FlyRotary] Re: Meredith Effect - Spitfire I'm wondering if that figure for airflow is true (2x airflow for water cooled vs air cooled).   All the measurements I have seen (not many) indicate that the exit air temperature on a Lyc installation is not significantly different than on our water cooled engines.   The total heat per HP is not that different so my assumption is that the CFM requirement is not much different.  The only advantage the air cooled engine's higher Dt gives you is that it requires far fewer square inches of surface area to transfer a given number of BTU with a given number of CFM.    Our advantage is that we can add surface area a LOT more easily than an air cooled can.  You can only put so many fins on a cylinder head. But I may be missing something.  Other thoughts? Tracy On Thu, Dec 24, 2009 at 3:38 PM, MONTY ROBERTS <montyr2157@windstream.net> wrote: Thomas, Though the Meredith effect is possible in theory if you actually run the numbers you find that the only time it would produce any thrust is at power levels in excess of 1000 hp and flight speeds over 400 mph. Even then the effect is very small and any gain you might get from it will be decimal dust compared to the drag from ingesting extra air. A liquid cooled engine will require ingesting roughly 2X the cooling air compared to an air cooled engine for the same power level. There is no
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